[RC5] Re: Is Rc5-64 taking forever?
b.ford at qut.edu.au
Mon Mar 9 11:39:31 EST 1998
It has been mentioned that we need to look at growth to get a true
estimate of time to complete RC5-64.
Using data from the two periods, 5-Dec-97 to 12-Jan-97 and 2-Mar-97
to 6-Mar-97, I did a regression assuming that we should have
exponential growth (and that that growth should have continued
through the DES II period). That regression gives a time to double
of ~275 days.
Moore's Law would give time to double of 18 months (365.25*1.5 =
I also looked at the possibility of recruiting reducing the time to
double to 180 days.
Time to double(days) Keyspace complete 50% keyspace complete
547.875 Jan 15, 2005 Jul 17, 2003
275 May 6, 2002 Aug 4, 2001
180 Mar 16, 2001 Sep 17, 2000
To me this shows that within 5 years, 64 bit RC5 encryption will not
be enough. If the doubling every 275 days was maintained for 5
years, d.n could exhaust an RC5-32/12/8 keyspace in 144 days.
Business(and others) need assurance that the standard of encryption
used will remain viable for much longer that 5 years.
"Time to move to a longer key length".
Bruce Ford b.ford at qut.edu.au
Teaching and Learning Support Services Ph: +61 7 3864 3383
Queensland University of Technology
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